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(No Model.) W. A. CAMPBELL.

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WM JYfwm illwrrnn STATES PATENT @rrreia WILLIAM A. CAMPBELL, OF EASTSAGINA\V, MICHIGAN, ASSIGNOR OF ONE- HALF TO A. F. BARTLETT & 00., OFSAME PLACE.

STEAM- BRAKE FOR SAW=lVllLL CARRlAGES.

SPECIFICATION forming part of Letters Patent No. 314,650, dated h iarch31, 1885.

Application filed September 24, 1884. (No model.)

description thereof, reference being had to the accompanying drawings,which form a part of this specification.

This invention relates to certain new and useful improvements insteam-brakes for saw- I mill carriages, and is designed to form animprovement on Letters Patent No. 301,091, dated July 1, 1884.

I The invention consists in an improved construction and arrangement ofthe parts, with the object in view to better control the operation ofthe brake.

In the drawings which accompany this specification, Figure 1 is anelevation of the brake, showing it as applied to the log carriage Ora.saw-mill. Fig. 2 is a vertical central cross-section of Fig. 1. Fig. 3is an elevation on the line 00 m of Fig. 1.

A is a T rail or flange, which is secured to the under side of the logcarriage, and parallel with the track upon which the carriagereciprocates. I

B B are the brake-levers, pivotally secured at a a, and operating in aplane at right angles to theT-rail, so that the brake-shoes O, which arepivotally secured to the upper ends of the short arms of the levers,arein proper position to grip the T-rail between them when the levers arespread apart upon their lower ends.

D is a steam-cylinder, pivotally suspended in any suitable mannervertically below the T-rail and between the two brake-levers B B, sothat its axial line is in the same vertical plane with the center linesof the levers, and equally divides the angle between them. Thisconstruction admits of the brakes being applied with equal effect, thecylinder yielding or turning on its pivotal point of suspension tocompensate for any defects which would otherwise cause one brake to beapplied with a greater force than the other, thereby pro ducing a strainupon the system which in course of time would produce serious results.

Eis the piston,and F is the piston-rod. The latter terminates in across-head, G, to which the inner ends of the toggle-levers H arepivotally secured. The outer ends of the toggle levers are pivotallysecured to the lower ends of the brake-levers.

I is a rod pivotally secured to the lower end of the cross-head G. Itpasses loosely through the cross-beam J, and has adjustably secured toits lower end, by means of the nut M, the rubber buffer K and counterweight L, the counter-weight L serving as a backing for the buffer K.

N is a steam chest. M is a pipe connecting said steam-chest with thelive steam. O is a pipe connecting it with the lower end of thecylinder, and P is the exhaust-pipe. This steam-chest contains a valveoperated by the valve-rod R in such manner that in one of its positionslive steam may be admitted into the cylinder, while in its alternateposition the steam previously introduced into the cylinder may beexhausted again.

The valve rod R is connected to one end of a bell-crank lever, S, theother end of which is connected to the vertical foot-shaft V,whichprojects through the floor and terminates in a foot-button, W,projecting sufficiently above the floor to allow the operator to operatethe valve with his foot. This foot-shaft is placed in proper position tobe operated by the sawyer. I

U is a counter-weight for keeping the valve normally open to theexhaust. Normally the valve is kept open to the exhaust by thecounter-weight U, and no live steam is admitted into the cylinder. Theweight of the piston and of the other parts connected thereto willtherefore keep the piston to the lower end of the cylinder and hold thebrake levers sufficientl y together upon their lower ends to bring thebrake-shoes out of contact with the T-rail, and the sawcarriage is freeto reciprocate.

Whenever the operator depresses the footbutton, the valve is reversedand steam is admitted below the piston. The piston in moving upward willnow actuate the toggle-levers and spread the lower ends of thebrakelevers apart, thus instantly applying the brakeshoes to the T-railand arresting the movement not interfere with the normal operation ofthe brake; but should the saw-carriage be at any time in aposition Wherethe T-rail runs out from between the brake-shoes the latter would bekept from closing much farther than they do in normal operation by thebuffer striking against the under side of the cross-girt. which acts as'a stop for the buffer. The object of this arrangement will be betterunderstood when it is considered that in order to get the necessarypower for braking, the upper ends of the brake-levers, to which thebrake-shoes are connected, are made as short as it can conveniently bedone, and therefore the T-rail would be removed from between thebrakeshoes. The little space created thereby would give the brake-leverssuch extended play that damage would be caused to the machinery.

In the construction described in the abovementioned Letters Patent, andfor which my improvement is especially designed, the piston wasinvariably blown out of the cylinder if'the brake was brought intooperation without the T-rail being between the brake-shoes. This couldnot be remedied by an increased length of cylinder, owing to thetransverse way the cylinder was placed between the brakelevers, andwhich did not admit of lengthening the cylinder. I have still introducedan additional measure of safety, which consists in the construction ofan air-cushion at the upper end of the cylinder, by means of the holes0, which allow the air to escape until the piston has far enough raisedto effect the braking. Any further advance of the piston will compressthe air in the cylinder above the holes a and cushion the piston.

The position in which I place the brakecylinder presents additionaladvantages over the one referred to. I apply the power more evenly tothe brake-levers and avoid all side strains. I gain greater leverage andcompactness by the use of the toggledevers, and also save muchdead-Weight or obviate the use of the springs by the increased facilitythe parts are given to return the piston to its normal condition whenthe brake is taken oft".

What I claim as my invention is 1. In a steam-brake operating asdescribed, the brake-cylinder D, pivotally and centrally suspendedbetween the two brake-levers B B,

and transmitting the breaking-power by means oftogglelevers connectingits piston-rod with the longer ends of the brake-levers, substantiallyas described.

2. In a steam-brake operating as described,

the combination of its brake-cylinder and pis- 'ton with thebuffer-block K, adjustably connected with said piston, and stop, as J,the parts being constructed and arranged to ar} rest the brakingmovement of the piston at anabnormal action of the same, substantially,

as described.

3. In a steam-brake, the combination of the two brake-levers B B andtheir brake-shoes O, of the brake-cylinder D, centrally suspendedbetween the brake-levers, of the cross head G, of the toggleelevers H,connecting the piston-rod with the brake-levers, of the red I, buffer K,counter-weight L, adjusting-screw,

and cross-girt, all combined substantially as and for the purposesdescribed.

WILLIAM A. CAMPBELL.

Witnesses: HERBERT A. FORREST, 9

WM. A. DONALDSON.

